Fig. 1

Capnograms classification from clinical observations. The figure illustrates the distribution of capnograms according to the classification. Each panel shows a typical CO₂ pattern obtained from clinical observations after numerical treatment from raw capnogram data (python, Python Software Foundation, Wilmington, Delaware, USA). X-axis represents inspiratory and expiratory time. A Intrathoracic airway closure: oscillations due to chest compressions and decompressions are small or absent. Lung volume reduction far below the FRC and complete or partial intrathoracic airway closure explain this specific capnogram. B Thoracic distension: oscillations due to chest compressions and decompressions are limited or absent at the beginning of the expiration phase and resume after a few chest compressions. Increase in lung volume due to large Vt insufflation before returning to FRC explains this specific capnogram. C Regular pattern: oscillations due to chest compressions and decompressions are clearly visible during the entire duration of the expiration phase. The regular pattern corresponds to the situation when neither thoracic distension nor intrathoracic airway closure is identified